WO2013140970A1 - Système de communication optique et procédé de communication optique ayant une haute résistance de bruit de phase - Google Patents

Système de communication optique et procédé de communication optique ayant une haute résistance de bruit de phase Download PDF

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WO2013140970A1
WO2013140970A1 PCT/JP2013/055266 JP2013055266W WO2013140970A1 WO 2013140970 A1 WO2013140970 A1 WO 2013140970A1 JP 2013055266 W JP2013055266 W JP 2013055266W WO 2013140970 A1 WO2013140970 A1 WO 2013140970A1
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optical
phase
signal
communication system
optical communication
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PCT/JP2013/055266
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English (en)
Japanese (ja)
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大作 小笠原
林　和則
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日本電気株式会社
国立大学法人京都大学
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Publication of WO2013140970A1 publication Critical patent/WO2013140970A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/548—Phase or frequency modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
    • H04B10/2543—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to fibre non-linearities, e.g. Kerr effect
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/616—Details of the electronic signal processing in coherent optical receivers
    • H04B10/6163—Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/60—Receivers
    • H04B10/61—Coherent receivers
    • H04B10/616—Details of the electronic signal processing in coherent optical receivers
    • H04B10/6165—Estimation of the phase of the received optical signal, phase error estimation or phase error correction

Definitions

  • the present invention relates to an optical communication system, and more particularly to an optical communication system having high phase noise tolerance.
  • the optical phase modulation method is a method in which data modulation is not performed only on the light intensity of the transmission laser light as in the conventional light intensity modulation method, but also on the optical phase of the transmission laser light.
  • BPSK Binary Phase Shift Keying
  • QPSK Quadrature Phase Shift Keying
  • 8PSK Quadrature Phase Shift Keying
  • QAM Quadrature Amplitude Modulation
  • 1 bit for example, 0, 1 is assigned to each of two optical phases (for example, 90 degrees and 180 degrees).
  • FIG. 1A is an example of a constellation diagram of BPSK.
  • QPSK 2 bits (for example, 00, 01, 11, 10) are allocated to four optical phases (for example, 45 degrees, 135 degrees, 225 degrees, and 315 degrees).
  • FIG. 1B is an example of a constellation diagram of QPSK.
  • the symbol rate of QPSK can be reduced to 1 ⁇ 2 of the symbol rate (that is, bit rate) of the light intensity modulation method.
  • the symbol rate that is, bit rate
  • the multi-level optical phase modulation method since a symbol rate (baud rate) can be lowered by assigning a plurality of bits to one symbol, the operation speed of an electric device can be reduced. Reduction of device manufacturing cost can be expected.
  • BPSK assigns 1 bit to one optical phase, and thus the above-mentioned effect cannot be obtained.
  • the distance between symbols is larger than other phase modulation methods, Since it has high tolerance against phase noise due to the nonlinear optical effect, it has a feature that it is suitable for a modulation system of an ultra-long distance optical communication system that transmits between continents.
  • signal light and laser light referred to as local oscillation light or local light
  • An optical coherent method is used in which the output is received by a photodetector after being coupled by an optical element.
  • the AC component of the electrical signal output from the photodetector is the signal when the optical coherent method is used. It is a beat signal of light and local oscillation light, its amplitude is proportional to the light intensity of the signal light and local oscillation light, and if the phase is the same as the carrier frequency of the signal light and the optical frequency of the local oscillation light, This is the difference in optical phase between the signal light and the local light. If the optical phase of the local oscillation light is the same as the optical phase of the laser beam input to the optical modulator at the transmission end, the beat signal phase is the optical phase added to the laser beam at the transmission end.
  • the value of the carrier frequency of the signal light and the value of the optical frequency of the local oscillation light do not completely match, and the optical phase of the local oscillation light at the receiver and the laser input to the optical modulator at the optical transmitter It does not match the optical phase of light. Therefore, it depends on the optical phase deviation which is the optical phase difference between the signal light and the local oscillation light input to the optical modulator in the optical transmitter, and the optical carrier frequency deviation which is the difference between the carrier frequency of the signal light and the optical frequency of the local light. The effect needs to be compensated.
  • polarization multiplexing / demultiplexing technology using digital signal processing is also attracting attention as one of the technologies for realizing an ultrahigh-speed optical communication system.
  • the polarization demultiplexing technique multiplexes two independent optical signals whose carrier waves are arranged in the same frequency band and whose polarization states are orthogonal to each other in the optical transmitter, and in the optical receiver, the received signal is multiplexed from the received signal.
  • This is a technology that realizes a double transmission speed by separating two independent optical signals. In other words, since the symbol rate (baud rate) of the optical signal can be halved, the operation speed of the electric device can be reduced and the apparatus cost can be reduced.
  • FIG. 2 is an example of a block diagram showing an optical transmitter 600 in a polarization multiplexed optical communication system using an optical digital coherent communication system.
  • the continuous light that is transmitted from the laser oscillator 101 at a predetermined optical frequency and branched into two is modulated by the drive signals transmitted from the drive signal transmission units 106-1 and 106-2 in the optical orthogonal modulators 102-1 and 102-2, respectively.
  • the drive signals are respectively generated by the signal generators 105-1 and 105-2 so as to be suitable for the optical phase modulation method from the transmission bit string. For example, in the case of BPSK or QPSK, a binary electric signal is generated, but when the multi-value number becomes large, such as 16QAM, it is necessary to generate a complex electric signal such as a quaternary value.
  • the drive signal transmitters 106-1 and 106-2 can be configured with only an amplifier when using an optical phase modulation method with a small multi-value number such as BPSK or QPSK, but when using a QAM with a large multi-value number, etc. Needs to be composed of a combination of a digital analog converter (DAC) and an amplifier.
  • the driving signal transmission units 106-1 and 106-2 transmit a real axis signal on the phase plane and a driving signal of an imaginary axis signal, respectively.
  • the output optical signal of the optical quadrature modulator 102-1 and the output optical signal of the optical quadrature modulator 102-2 are multiplexed in a state where the polarization states are orthogonal to each other in the polarization multiplexing unit 103.
  • FIG. 3 is an example of a block diagram showing a configuration of an optical receiver 700 in an optical communication system using an optical digital coherent communication system.
  • the optical signal received from the optical transmission line is input to the 90-degree optical hybrid 201 together with the local oscillation light having an optical frequency substantially the same as the carrier frequency of the received optical signal.
  • the 90-degree optical hybrid 201 outputs a total of four optical signals of a real part component and an imaginary part component of an optical signal having a polarization state parallel to each of two orthogonal polarization axes.
  • optical signals are converted into analog electric signals by the optical detectors 202-1 to 202-1, and then converted into digital electric signals by the analog-digital converters (ADC) 203-1 to 20.
  • ADC analog-digital converters
  • These digital electrical signals are converted into digital electrical signals sampled at the symbol rate of the received optical signal by a resampling unit (not shown in FIG. 3), and then input to the chromatic dispersion compensation unit 209.
  • the chromatic dispersion compensation unit 209 compensates for waveform distortion due to chromatic dispersion by setting the residual chromatic dispersion of received light to zero.
  • the signal data in which the waveform distortion due to wavelength dispersion is compensated is input to the polarization separation unit 204.
  • the polarization separation unit 204 extracts two independent optical signals that are polarization multiplexed based on the four input digital electrical signals. Each of the extracted optical signals is compensated by the optical carrier frequency deviation / optical phase deviation compensation units 205-1 and 205-2 for optical phase rotation due to optical carrier frequency deviation and optical phase deviation between the received optical signal and the local oscillation light. After that, the symbol identifying sections 206-1 and 206-2 demodulate the original transmission bit strings, respectively. As described above, after combining optical phase modulation and polarization demultiplexing technology, the effects of optical carrier frequency deviation and optical phase deviation are compensated for each of the two independent optical signals that have undergone polarization separation. By doing so, it becomes possible to realize an ultra-high-speed optical communication system exceeding 100 Gbps per channel.
  • This type of optical communication system is also disclosed in Patent Documents 1 and 2, for example.
  • the optical receiver disclosed in Patent Document 1 performs fast Fourier transform on a time domain received signal, performs frequency equalization on a frequency domain component, and returns the time domain signal by inverse fast Fourier transform.
  • the optical signal transmission device disclosed in Patent Document 2 performs chromatic dispersion pre-equalization on signal light.
  • Patent Document 3 in order to improve the bit error rate by removing the influence of intersymbol interference, fast Fourier transform is performed on the received signal in the time domain, frequency equalization is performed on the frequency domain component, A wireless terminal that returns to a time domain signal by inverse fast Fourier transform is disclosed.
  • phase noise increases as the magnitude (line width) of the oscillation frequency fluctuates, and the inter-symbol distance decreases as the multi-value number of the optical signal modulation method increases.
  • an object of the present invention is to provide an optical communication system having high phase noise tolerance.
  • the optical transmitter includes an optical transmitter that modulates and transmits an optical signal at a predetermined symbol interval, and an optical receiver that receives the optical signal.
  • the optical transmitter is an electrical signal corresponding to a bit string.
  • a signal processing unit that generates a signal having a transmission characteristic in which an impulse response length is equal to or greater than the symbol interval, and applies a phase change corresponding to a frequency to the transmission light of the optical transmitter to the generated electrical signal
  • a phase adding unit to be implemented; a driving unit that generates a driving signal in accordance with the filtered electrical signal; a light source that outputs continuous light; and the continuous light is modulated based on the driving signal and transmitted.
  • a modulation unit that outputs light, and the optical receiver is included in the photoelectric conversion unit that converts the optical signal transmitted from the optical transmitter into an electrical signal, and the converted electrical signal,
  • the phase change given by the phase adder The optical communication system is obtained, characterized in that it comprises a phase compensation unit for amortization.
  • a light output step of outputting continuous light from a light source in the optical device, a modulation step of modulating the continuous light based on the drive signal in the optical transmitter and outputting transmission light, and A photoelectric conversion step for converting the optical signal transmitted from the optical transmitter into an electric signal, and a phase change given in the phase addition step included in the converted electric signal in the optical receiver are compensated.
  • the optical communication system according to the present invention has improved phase noise tolerance of optical signals.
  • FIG. 1A is a BPSK constellation diagram
  • FIG. 1B is a QPSK constellation diagram
  • FIG. 2 is a block diagram showing a configuration of an optical transmitter in an optical communication system using an optical digital coherent communication system according to a related technique.
  • FIG. 3 is a block diagram showing a configuration of an optical receiver in an optical communication system using an optical digital coherent communication system according to a related technique.
  • FIG. 4 is a block diagram showing the configuration of the optical transmitter in the optical communication system using the optical digital coherent communication system according to the first embodiment of the present invention.
  • FIG. 5 is a block diagram showing the configuration of the optical receiver in the optical communication system using the optical digital coherent communication system according to the first embodiment of the present invention.
  • FIG. 6A is a QPSK constellation diagram of an optical communication system according to the related art
  • FIG. 6B is a QPSK constellation diagram of an optical communication system according to the present invention
  • FIG. 7 is a block diagram showing the configuration of the optical transmitter in the optical communication system using the optical digital coherent communication system according to the second embodiment of the present invention
  • FIG. 8 is a block diagram showing the configuration of the optical receiver in the optical communication system using the optical digital coherent communication system according to the second embodiment of the present invention.
  • FIG. 4 is a block diagram showing the configuration of the optical transmitter 100 in the first embodiment of the present invention.
  • an optical transmitter 100 is an optical transmitter in an optical communication system using an optical digital coherent communication system, and a laser oscillator 101 that transmits continuous light at a predetermined optical frequency, and phase modulation from a transmission bit string.
  • a signal generation unit 105 that generates a drive signal so as to be suitable for the system, and a drive signal transmission unit 106 that transmits at least a drive signal based on a signal obtained from the signal generation unit 105 via a phase addition unit 107 described later.
  • an optical quadrature modulator 102 that QPSK-modulates the continuous light transmitted from the laser oscillator 101 with the drive signal from the drive signal transmission unit 106.
  • the optical transmitter 100 is further based on the chromatic dispersion that the optical signal output from the optical quadrature modulator 102 will receive during transmission with respect to the electrical signal generated by the signal generation unit 105.
  • a chromatic dispersion pre-equalization unit that performs filter processing for adding a phase according to frequency may be included.
  • the optical transmitter 100 in the present embodiment differs from the configuration of the optical transmitter 600 according to the related art shown in FIG. 2 in that a phase adding unit 107 that adds a phase change to a transmission optical signal And a first phase setting unit 108 for setting a phase change with respect to the phase adding unit 107. Note that the first phase setting unit 108 is not necessarily provided.
  • an optical receiver 200 is an optical receiver in an optical communication system using an optical digital coherent communication system, and an optical detector 202 that converts an optical signal received from an optical transmission path into an analog electric signal; Based on an analog-digital converter (ADC) 203 that converts an analog electrical signal transmitted from the optical detector 202 into a digital electrical signal, and a digital electrical signal that is input from the ADC 203 via a phase compensation unit 207 described later, residual chromatic dispersion is achieved.
  • ADC analog-digital converter
  • An optical carrier wave that compensates for optical phase rotation due to optical carrier frequency deviation and optical phase deviation between the received optical signal and the local oscillation light, from the chromatic dispersion compensation unit 209 that compensates, and the signal data from which the waveform distortion due to chromatic dispersion has been removed Frequency deviation / optical phase deviation compensation unit 205 and optical carrier frequency deviation / optical phase deviation compensation unit 2
  • the chromatic dispersion compensator 209 gives each wavelength component included in the input signal from the phase compensator 207 a different amplification factor and delay amount by a plurality of taps, and then combines the components to thereby combine the wavelengths. Waveform distortion due to chromatic dispersion is removed.
  • the optical receiver 200 in the present embodiment is different from the configuration of the optical receiver 700 according to the related art shown in FIG. 3, and includes a phase compensation unit 207 that adds a phase change to the received electric signal. And a second phase setting unit 208 that sets a phase change with respect to the phase compensation unit 207. Note that the second phase setting unit 208 is not necessarily provided.
  • the phase adding unit 107 of the optical transmitter 100 performs a Fourier transform process on the time domain signal generated by the signal generating unit 105 and then performs a predetermined amount of phase change on each frequency component of the signal.
  • the signal is reconverted into a time domain signal by an inverse Fourier transform process.
  • the signal to which the predetermined amount of phase change is added is supplied to the optical quadrature modulator 102 by the drive signal transmission unit 106 as in the related art described above. If the signal generated by the signal generation unit 105 is a signal in the frequency domain, the above-described Fourier transform process can be omitted.
  • the magnitude of the phase change added to the signal in the phase adding unit 107 is the time spread (phase phase) of the signal output from the phase adding unit 107 when an impulse signal is used as the signal input to the phase adding unit 107.
  • the impulse response length of the transfer characteristic of the adding unit 107 is required to be at least larger than the symbol interval of the optical signal.
  • the finite resource includes, for example, the number of filter coefficients of the filters that constitute the phase adding unit 107. That is, the magnitude of the phase fluctuation is controlled so that the time spread of the signal output from the phase adding unit 107 is made as large as possible with respect to the number of filter coefficients of the filters constituting the phase adding unit 107.
  • Equation (1) can be used as the phase change amount that maximizes the impulse response length of the transfer characteristic of the phase adding unit 107.
  • ⁇ k is the phase change amount of each frequency component
  • k is an integer of 0 to M
  • M is the window size of the Fourier transform process or inverse Fourier transform process.
  • Equation (1) can be derived on condition that the entropy H defined by the following equation (2) is maximized.
  • h i is an impulse response of the phase adding unit 107.
  • the phase compensator 207 of the optical receiver 200 performs Fourier transform processing on the received signal in the time domain, and then drives each frequency component of the received signal in the phase adder 107 of the optical transmitter 100. After adding a phase change amount having the same magnitude and a different sign from the phase change added to each frequency component of the signal, it is reconverted into a time domain received signal by inverse Fourier transform processing.
  • the received signal to which a predetermined amount of phase change is added is supplied to the chromatic dispersion compensation unit 209.
  • phase compensation unit 207 since the phase change added by the optical transmitter 100 is compensated by the phase compensation unit 207, the subsequent demodulation processing can be performed in the same manner as a conventional optical receiver. It should be noted that chromatic dispersion pre-equalization for adding chromatic dispersion in the optical transmitter can be performed simultaneously with the phase addition of the present invention by the phase adding unit 107, and the residual chromatic dispersion of the received light in the optical receiver.
  • the phase compensation unit 207 can be implemented simultaneously with the phase compensation of the present invention. In this case, an effect of reducing power consumption can be obtained by reducing the circuit scale of the LSI realizing the present invention. The effect of improving the phase noise tolerance by applying the present invention is shown in FIG. FIG.
  • FIG. 6A is a constellation diagram of a QPSK signal received by adding phase noise in the related art transmitter / receiver 700 described above as a comparative example.
  • FIG. 6B shows a case where the transceiver 200 of the present invention is used.
  • the constellation of the QPSK signal shown in FIG. 6A has a larger symbol spread in the phase direction due to phase noise than the symbol spread in the polar direction.
  • the constellation of the QPSK signal shown in FIG. 6B has substantially the same symbol spread in the polar and phase directions, and the present invention can reduce the symbol spread in the phase direction due to phase noise. I understand.
  • FIG. 7 is a block diagram showing the configuration of the optical transmitter 300 in the second embodiment of the present invention.
  • an optical transmitter 300 is an optical transmitter in a polarization multiplexed optical communication system using an optical digital coherent communication system, as in the related art shown in FIG. 2, and is continuously transmitted at a predetermined optical frequency.
  • the laser oscillator 101 that transmits light, the signal generation units 105-1 and 10-2 that generate drive signals from the transmission bit string so as to be suitable for the phase modulation method, and at least an amplifier, are described below from the signal generation units 105-1 and 105-2.
  • Driving signal transmitting units 106-1 to 106-2 for transmitting a driving signal based on signals obtained through the phase adding units 107-1 to 107-2, and continuous light branched from the laser oscillator 101.
  • Optical quadrature modulators 102-1 and 102-2 that perform QPSK modulation using the drive signals from the signal transmitters 106-1 and 106-2, respectively, and states in which their polarization states are orthogonal to each other After having multiplexed, and a polarization multiplexing unit 103 to be output to the optical transmission path.
  • the optical transmitter 300 further transmits the optical signals output from the optical quadrature modulators 102-1 and 102-2 to the electrical signals generated by the signal generators 105-1 and 105-2.
  • FIG. 8 is a block diagram showing the configuration of the optical receiver 400 in the embodiment of the present invention.
  • an optical receiver 400 is an optical receiver in a polarization multiplexed optical communication system using an optical digital coherent communication system, as in the related art shown in FIG.
  • a 90-degree optical hybrid 201 that outputs a total of four optical signals
  • optical detectors 202-1 to 202-4 that convert the four optical signals transmitted from the 90-degree optical hybrid 201 into analog electrical signals
  • an optical detector respectively.
  • Analog-to-digital converter (ADC) 2 for converting the four analog electric signals sent from 202-1 to 202-4 into digital electric signals, respectively.
  • chromatic dispersion compensation unit 209 that compensates for residual chromatic dispersion based on four digital electric signals input from ADCs 203-1 to 207 through phase compensation unit 207, which will be described later, and chromatic dispersion A polarization separation unit 204 that extracts two independent optical signals polarization-multiplexed from the signal data from which the waveform distortion has been removed, and an optical carrier frequency between the received optical signal and the local oscillation light, respectively.
  • Optical carrier frequency deviation / optical phase deviation compensation units 205-1 and 20-2 that compensate for optical phase rotation due to deviation and optical phase deviation, and signals from optical carrier frequency deviation and optical phase deviation compensation units 205-1 and 205-2, Symbol identifying units 206-1 and 206-2 that demodulate the original transmission bit string.
  • the chromatic dispersion compensator 209 gives each wavelength component included in the input signal from the phase compensator 207 a different amplification factor and delay amount by a plurality of taps, and then combines the components to thereby combine the wavelengths. Waveform distortion due to chromatic dispersion is removed.
  • the optical receiver 400 in this embodiment differs from the configuration of the optical receiver 700 according to the related art shown in FIG.
  • phase compensation unit 207 that adds a phase change to the received electric signal.
  • second phase setting unit 208 that sets a phase change with respect to the phase compensation unit 207. Note that the second phase setting unit 208 is not necessarily provided.
  • the Fourier transform processing is performed on the time domain signals generated by the signal generation units 105-1 and 105-2, and then each frequency component of the signal is converted.
  • the signal is reconverted into a time domain signal by inverse Fourier transform processing.
  • Signals to which a predetermined amount of phase change is added are supplied to the optical quadrature modulators 102-1 and 102-2 by the drive signal transmission units 106-1 and 106-2, as in the related art described above.
  • the signals generated by the signal generators 105-1 to 105-2 are signals in the frequency domain, the above-described Fourier transform process can be omitted.
  • the magnitude of the phase change added to the signal in the phase adding units 107-1 and 107-2 is the same as that in the case where an impulse signal is used as the signal input to the phase adding units 107-1 and 107-2.
  • the time spread of the signal output from ⁇ 2 impulse response length of the transfer characteristic of the phase adding units 107-1 and 107-2) needs to be larger than at least the symbol interval of the optical signal.
  • the finite resource includes, for example, the number of filter coefficients of the filters constituting the phase adding units 107-1 and 107-2.
  • Equation (3) can be used as the phase change amount that maximizes the impulse response length of the transfer characteristics of the phase adding units 107-1 and 107-2.
  • ⁇ k is a phase change amount of each frequency component
  • k is an integer of 0 or more and M or less
  • M is a window size of the Fourier transform process or the inverse Fourier transform process. Equation (3) can be derived on condition that the entropy H defined by the following equation (4) is maximized.
  • h i is an impulse response of the phase adding units 107-1 and 107-2.
  • the method for generating the transmission optical signal of the present invention using digital signal processing has been described above. However, if there is an optical device capable of adding the same phase change as the above-described phase change, the transmission optical signal of the present invention is thereby determined. Can also be generated.
  • a method for demodulating a signal using the optical receiver 400 of the present invention will be described. In the phase compensation unit 207 of the optical receiver 400, the Fourier transform processing is performed on the received signal in the time domain, and then the phase adding unit 107-1 of the optical transmitter 300 is applied to each frequency component of the received signal.
  • phase change added by the optical transmitter 300 is compensated by the phase compensation unit 207, the demodulation processing after the polarization separation unit 204 can be performed in the same manner as a conventional optical receiver.
  • chromatic dispersion pre-equalization for adding chromatic dispersion in the optical transmitter can be performed simultaneously with the phase addition of the present invention by the phase adding units 107-1 and 107-2. Residual chromatic dispersion can be performed simultaneously with the phase compensation of the present invention by the phase compensation unit 207. In this case, an effect of reducing power consumption can be obtained by reducing the circuit scale of the LSI realizing the present invention.
  • the phase adding unit 107 in the optical transmitter 100 of the first embodiment and the optical transmitter 300 of the second embodiment can be configured using an FIR filter (Finite Impulse Response filter). That is, it is possible to generate a drive signal by filtering a time domain signal using an FIR filter having a filter coefficient as a value obtained by performing an inverse Fourier transform process on a phase change in the frequency domain.
  • FIR filter Finite Impulse Response filter
  • the optical transmitter is A signal generator for generating an electrical signal corresponding to the bit string;
  • a phase adding unit that has a transmission characteristic in which an impulse response length is equal to or greater than the symbol interval, and that performs a filtering process on the generated electric signal to apply a phase change corresponding to a frequency to the transmission light of the optical transmitter;
  • a drive unit that generates a drive signal according to the electrical signal subjected to the filtering process;
  • a light source that outputs continuous light;
  • a modulator that modulates the continuous light based on the drive signal and outputs transmission light;
  • the optical receiver is: A photoelectric converter that converts the optical signal transmitted from the optical transmitter into an electrical signal;
  • An optical communication system comprising: a phase compensation unit that compensates for a phase change provided by the phase addition unit included in the converted electrical signal.
  • the phase addition unit generates a filter process for adding a phase corresponding to the frequency so as to maximize the impulse response length with respect to the number of filter coefficients of the phase addition unit that performs the filter process.
  • the optical communication system according to appendix 1 which is performed on the electrical signal.
  • the phase adding unit is configured to maximize entropy defined by a value obtained by adding a negative sign to a sum of products of amplitude squares of coefficients of the impulse response and a logarithmic value based on 2 of the square of the amplitude.
  • the optical communication system according to appendix 1, wherein filtering processing for adding a phase corresponding to the frequency to the generated electrical signal is performed.
  • the optical communication system according to appendix 4 wherein the phase adding unit performs a filtering process for further adding a phase corresponding to a frequency based on chromatic dispersion that the optical signal receives during transmission to the generated electric signal.
  • the optical transmitter further includes a first phase setting unit that sets a phase change with respect to the phase adding unit, 6.
  • the optical receiver further includes a second phase setting unit that sets a phase change with respect to the phase compensation unit.
  • the present invention is not limited to the embodiments described above, and it goes without saying that various modifications are possible within the technical scope described in the claims.
  • the phase change addition means and the compensation means are not necessarily digital signal processing. Need not be.
  • the present invention is also applicable to an optical communication system that uses a single-polarized optical signal that is not polarization multiplexed.
  • this application claims its benefit on the basis of priority from Japanese Patent Application No. 2012-066543 filed on March 22, 2012, the disclosure of which is hereby incorporated herein in its entirety Incorporated as a reference.

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  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

La présente invention se rapporte à un système de communication optique, grâce auquel la résistance de bruit de phase d'un signal optique est améliorée. Ce système de communication optique comprend un appareil de transmission optique qui transmet un signal optique qui est décalé en phase à un intervalle de symbole prédéterminé et un appareil de réception optique qui reçoit le signal optique. Le dispositif de transmission optique comprend en outre une unité d'ajout de phase. L'unité d'ajout de phase a une caractéristique de transmission dans laquelle une longueur de réponse impulsionnelle est supérieure ou égale à l'intervalle de symbole et effectue sur un signal électrique généré un processus de filtrage qui applique un changement de phase sur la lumière transmise de l'appareil de transmission optique en fonction de la fréquence de celui-ci. L'appareil de réception de lumière comprend en outre une unité de correction de phase. La phase unité de correction corrige le décalage de phase qui est appliqué dans l'appareil de transmission optique et qui est inclus dans le signal électrique déphasé.
PCT/JP2013/055266 2012-03-22 2013-02-21 Système de communication optique et procédé de communication optique ayant une haute résistance de bruit de phase WO2013140970A1 (fr)

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* Cited by examiner, † Cited by third party
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CN103916189A (zh) * 2014-04-22 2014-07-09 山西大学 在光纤传输中压缩低频相位噪声的方法
CN103916189B (zh) * 2014-04-22 2016-05-11 山西大学 在光纤传输中压缩低频相位噪声的方法
JP2021057787A (ja) * 2019-09-30 2021-04-08 沖電気工業株式会社 信号変換装置、変調装置、信号逆変換装置、復調装置、変調方法、復調方法及び伝送装置
CN114844574A (zh) * 2022-07-04 2022-08-02 浙江大学湖州研究院 一种光纤通信系统及通信方法

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